a. Field of the Invention
The present invention relates to a drive mechanism and a head rail for a blind, in particular to a drive mechanism and head rail allowing tilting and retraction of the blind slats.
b. Background Art
Previously, it was known to provide a vertical blind suspended from a head rail for covering an architectural opening. Each vertical slat is suspended from a carriage which is movable towards and away from one end of the head rail. Traditionally, some form of chain or cord extends in a loop along the length of the head rail so as to retract and deploy the carriages. Furthermore, a rotatable rod also extends the length of the head rail and rotation of the rod is transferred by the carriages so as to rotate the vertical slats.
Traditionally, the two operations of tilting and retraction are controlled by separate cords or chains hanging down from the head rail. However, EP-A-0467627 discloses a system by which both operations may be controlled by means of a single cord. In particular, a lost motion mechanism is provided between an input wheel driven by the control cord and drive to the retraction mechanism. Furthermore, slip is allowed to occur between the input control wheel and the tilt mechanism once the slats have reached their full tilt in either direction. In this way, movement of the control cord will first operate the tilt mechanism and then, once the slats have been fully tilted and the lost motion mechanism has come to the end of its travel, the slats are either retracted or deployed.
It has also been proposed to control blind movement by means of a motor, for instance in DE-U-9406083. However, this creates additional problems. The provision of two motors and associated control for the two slat operations is unduly bulky, heavy and expensive. Furthermore, the provision of a single motor with appropriate servo operation to direct power selectively to the two slat operations is also unduly complicated and expensive. With respect to the system of EP-A-0467627, it is undesirable to use a motor in conjunction with the slip mechanism provided for the tilt of slats, since the force required for slip needs to be carefully matched to the torque available from the motor. Indeed, even for manual cord operation, the slip mechanism is undesirable, because of the associated wear of its components.
According to the present invention, there is provided a head rail for a vertical blind, the head rail being elongate and having a mechanism at one end for selectively tilting and retracting slats of the vertical blind along the length of the head rail, the mechanism having a control gear, the rotation of which affects the selective tilting and retracting, wherein the control gear is located at a position along the length of the head rail so that it can be meshed with teeth of an external drive source.
In this way, the head rail may be constructed independently of any power source. A single head rail may be fitted with different power sources according to requirements. For instance, motor units may be provided which are operated remotely or by means of cords. Alternatively, a manually operated mechanism, for instance with cords, may be provided as the drive source.
Similarly, different types and lengths of head rail may be provided and all be useable with the same drive source.
Preferably, the head rail includes a housing forming a generally enclosed structure, the housing including an aperture by which the control gear may mesh with the teeth of an external drive source. In this respect, the control gear can be rotatable about an axis parallel to the extent of the head rail.
In this way, an aesthetically pleasing head rail may be provided. In particular, the head rail can include a housing to conceal all of the various operating parts of the head rail. However, by providing an aperture for the control gear, the head rail can still be operated by an external drive source.
Preferably, the aperture is located in the housing such that it is generally not visible in use. In this respect, the housing can have an elongate surface from which the slats may extend, for instance a lower surface, and at least one other parallel elongate surface, for instance a back surface, in which the aperture is formed.
Preferably the mechanism has another control gear, the rotation of which affects the selective tilting and retracting, the housing has another parallel elongate surface in which another aperture is formed by which the control gear may be operated by the teeth of an external drive source.
The same control gear may be meshed with the teeth of the external drive source, or the mechanism may have another control gear as part of a gear train which affects the selective tilting and retracting. In this case, the another control gear may mesh with the teeth of the external drive source.
In this way, flexibility is provided in the way in which the external drive source may be mounted to the head rail. In particular, the second aperture and control gear may be provided towards the upper surface of the head rail.
According to the present invention, there is also provided a head rail as described above in combination with a motor unit for attachment to the at least one other parallel elongate surface of the head rail, the motor unit having a toothed drive gear for meshing with the control gear.
Preferably, the motor unit is a generally elongate structure having an elongate attachment surface for mounting alongside the at least one other parallel elongate surface.
A latch and clip arrangement may be provided as defined in the appended claims for attaching the motor unit to the head rail.
According to the present invention, there is also provided a drive mechanism for a blind having an array of retractable and tiltable slats, the mechanism including:
a rotatable tilt drive for tilting slats;
a rotatable retract drive for retracting and deploying slats; and
a transmission for rotating the tilt drive and the retract drive by means of a single rotatable source; wherein
the transmission includes a clutch for rotating the tilt drive, the clutch incorporating a first lost motion mechanism whereby, after a predetermined number of rotations in the same direction, transmission by the clutch to the tilt drive is disengaged.
In this way, both the tilt and retract operations of a blind may be controlled from a single rotatable source. Furthermore, by means of the lost motion mechanism and clutch, drive to the tilt mechanism is completely disengaged during drive of the retract mechanism. Hence, undue load on the drive source is avoided, together with wear of any components which were required to slip according to previous arrangements.
The drive mechanism is particularly advantageous in conjunction with the head rail defined above, since it provides the single control gear for operation by a drive source.
Preferably, the clutch comprises a cylindrical drive surface to be driven by the single rotatable source and a wrap spring such as a coil spring arranged to grip the drive surface, the wrap spring having radially extending ends for rotating the tilt drive.
The lost motion mechanism can include respective wrap spring release surfaces adjacent the ends of the wrap spring such that, when the wrap spring release surfaces are prevented from rotating and an end of the wrap spring rotates into abutment with a respective one of the wrap spring release surfaces, the wrap spring is resiliently deformed so as to release the grip on the drive surface.
In this way, transmission from the rotatable source to the tilt drive passes through the wrap spring and by using the wrap spring release surfaces to deform the wrap spring, drive to the wrap spring from the drive surface is disengaged.
In contrast, the tilt drive includes respective tilt surfaces adjacent the ends of the wrap spring such that, when an end of the wrap spring is rotated into abutment with a respective tilt surface, the grip of the wrap spring on the drive surface is tightened and the tilt drive is rotated.
In this way, the wrap spring passes drive from the drive surface to the tilt surfaces so as to rotate the tilt drive.
Preferably, the wrap spring surrounds the drive surface and the ends of the wrap spring extend radially outwardly. The wrap spring release surfaces and tilt surfaces are then formed on the edges of components extending axially around the outer periphery of the wrap spring and adjacent its ends.
The lost motion mechanism may include a series of co-axial wheels each constrained to be rotatable relative to an adjacent wheel through only a limited extent.
Alternative lost motion mechanisms may also be provided so as to allow only a limited amount of rotation of the wrap spring release surfaces. Indeed, according to the present invention, there may be provided a lost motion mechanism comprising first and second components relatively rotatable about a common axis;
a spacer disposed between the first and second components; and
a flexible elongate member having ends attached respectively to the first and second components wherein relative rotation of the first and second components causes the flexible elongate member to wrap around the spacer such that the first and second components can rotate relative to one another by an amount determined by the length of the flexible elongate member.
The first lost motion mechanism may be such a lost motion mechanism.
Preferably, the retract drive is rotated by the transmission by means of a second or retract lost motion mechanism such that the retract drive is only rotated after a predetermined number of rotations of the transmission in the same direction.
In this way, the retract drive is not operated during initial operation of the tilt drive.
Preferably, the retract lost motion mechanism has a greater extent of lost motion than the tilt lost motion mechanism such that transmission to the tilt drive is disengaged before transmission is provided to the retract drive.
In this way, slats of the blind may be fully tilted and their drive disengaged before any retraction or deployment starts.
The second lost motion mechanism may comprise first and second components relatively rotatable about a common axis;
a spacer disposed between the first and second components; and
a flexible elongate member having ends attached respectively to the first and second components wherein relative rotation of the first and second components causes the flexible elongate member to wrap around the spacer such that the first and second components can rotate relative to one another by an amount determined by the length of the flexible elongate member.
According to the present invention, there is provided a drive mechanism for a blind comprising:
an output gear rotatable relative to a housing for at least one of moving and tilting blind slats;
a planet gear mating with the output gear;
an input drive rotatable by a user for moving the planet gear in a circular path around the output gear; wherein
the planet gear is restrained to limited rotation relative to the housing such that rotation of the input drive causes rotation of the output gear, but the output gear is unable to transmit drive back through to the input drive.
In this way, a user may provide drive to move or tilt the blind slats such that the blind slats will remain securely in the position in which they are left. In particular, the weight of the blind slats or any attempt to move them will cause the drive mechanism to lock up, thereby preventing any motion.
Preferably, this drive mechanism may be used in conjunction with the mechanisms described above in respect of one or both of the tilt and retract operations.